Key result
Carotid and femoral Doppler flows fail to reliably detect fluid responsiveness during passive leg raising.
Why the study?
The hemodynamic effects of the passive leg raising test must be assessed through direct measurement of cardiac index, but the reliability of Doppler common carotid and femoral artery blood flow measurements for this purpose was uncertain.
Do Doppler measurements of carotid and femoral blood flow accurately detect a positive passive leg raising test compared to direct cardiac index measurement?
Observational (n=33)
No
Do Doppler measurements of carotid and femoral blood flow accurately detect a positive passive leg raising test compared to direct cardiac index measurement?
Effect estimate: AUC 0.58
p-value: p=0.62
Doppler measurements of carotid and femoral blood flow are not reliable surrogates for assessing cardiac output changes during a passive leg raising test.
Carotid/femoral Doppler flows should not guide PLR assessment; leaves open whether refined noninvasive surrogates can reliably track CI changes.
BACKGROUND: The hemodynamic effects of the passive leg raising (PLR) test must be assessed through a direct measurement of cardiac index (CI). We tested whether changes in Doppler common carotid blood flow (CBF) and common femoral artery blood flow (FBF) could detect a positive PLR test (increase in CI ≥ 10%). We also tested whether CBF and FBF changes could track simultaneous changes in CI during PLR and volume expansion. In 51 cases, we measured CI (PiCCO2), CBF and FBF before and during a PLR test (one performed for CBF and another for FBF measurements) and before and after volume expansion, which was performed if PLR was positive. RESULTS: Due to poor echogenicity or insufficient Doppler signal quality, CBF could be measured in 39 cases and FBF in only 14 cases. A positive PLR response could not be detected by changes in CBF, FBF, carotid nor by femoral peak systolic velocities (areas under the receiver operating characteristic curves: 0.58 ± 0.10, 0.57 ± 0.16, 0.56 ± 0.09 and 0.64 ± 10, respectively, all not different from 0.50). The correlations between simultaneous changes in CI and CBF and in CI and FBF during PLR and volume expansion were not significant (p = 0.41 and p = 0.27, respectively). CONCLUSION: Doppler measurements of CBF and of FBF, as well as measurements of their peak velocities, are not reliable to assess cardiac output and its changes.
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Girotto et al. (2018) conducted an observational in Critically ill patients requiring hemodynamic monitoring (n=33). Doppler measurement of carotid and femoral blood flow vs. Pulse contour analysis-derived cardiac index was evaluated on Ability of changes in carotid blood flow to detect a positive passive leg raising test (cardiac index increase ≥ 10%) (AUC 0.58, p=0.62). Doppler measurements of carotid and femoral blood flows failed to reliably detect a positive response to a passive leg raising test, with areas under the ROC curve not significantly different from 0.50.
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